More details are being released regarding a deadly amphibious assault vehicle accident in Southern California on July 30.

1 Marine has died, 8 service members remain missing and 2 were injured after an AAV mishap July 30 off the coast of Southern California. All are assigned to the 15th Marine Expeditionary Unit. Search and rescue efforts are still underway with support from the Navy and Coast Guard.

The incident occurred around 5:45 p.m. local time near the northwest part of San Clemente Island, the Navy-owned piece of land 80 miles off the coast of Southern California. The island is used by the Navy and Marine Corps for training.

Seven of the personnel were able to get out of the sinking land- and sea-going vehicle and were pulled from the water. Medics took three of them to Scripps Memorial Hospital La Jolla, where one was pronounced dead and the others were admitted in critical but stable condition.

“We continue search and rescue efforts off the coast of California for those involved in the tragic AAV mishap,”  Gen. David H. Berger, Commandant of the Marine Corps, said.

Officials said it was unclear how the accident happened. The Navy and the Coast Guard were assisting in the search for the missing service members, the force said, and AAV water operations have been suspended while the Marine Corps performs an investigation into the accident.

“Representatives have notified all families of the Marines and Sailor involved in Thursday’s tragedy,” the Marines said early Friday “We have covered more than 200 square nautical miles in the extensive search for our 8 missing service members.”

The 26-ton amphibious vehicle went down more than 1,000 yards from a beach on the northwest side of the island in water several hundred feet deep, Lt. Gen. Joseph Osterman, commanding general of I Marine Expeditionary Force said.

“It’s really below the depth that a diver can go to,” Osterman told reporters.

A Tweet from the First MEF reads “We are deeply saddened by this tragic incident. I ask that you keep our Marines, Sailors, and their families in your prayers as we continue our search,” said Col. Christopher Bronzi, 15th MEU Commanding Officer.